Simple model of coherent anti‐Stokes Raman scattering signals generated by means of linearly chirped ultrashort Gaussian laser pulses

Marrocco, Michele

doi:10.1002/jrs.5373

Cited by 6 publications

(19 citation statements)

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“…Marrocco presented a simple model of CARS signals generated by means of linearly chirped ultrashort Gaussian laser pulses. Comparison with known experiments shows a good agreement except for some limitations imposed by deviations of the nonresonant CARS signal from the Gaussian structure assumed in the model …”

Section: Nonlinear Coherent and Time‐resolved Raman Spectroscopymentioning

confidence: 54%

Recent advances in linear and nonlinear Raman spectroscopy. Part XIII

Nafie

2019

J Raman Spectroscopy

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This article is an overview of advances in Raman spectroscopy published in 2018 in the Journal of Raman Spectroscopy (JRS) and, in addition, trends over the past decade across journals that have published papers important to the field of Raman spectroscopy. The trends are based on statistical data of article counts obtained from Clarivate Analytic's Web of Science Core Collection byyear and by subfield of Raman spectroscopy. Coverage is provided for presentations involving Raman spectroscopy at four international conferences this published in JRS in 2018 are highlighted and arragned by topics at the frontier of Raman spectroscopy. Based on these data, presentations, and publications, it is clear that Raman spectroscopy continues as an expanding field of research across a wide range of novel disciplines and applications that provide sensitive photonic information at the molecular level.KEYWORDS advances in Raman spectroscopy, applications of Raman spectroscopy, developments in Raman spectroscopy, review

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Section: Nonlinear Coherent and Time‐resolved Raman Spectroscopymentioning

confidence: 54%

Recent advances in linear and nonlinear Raman spectroscopy. Part XIII

Nafie

2019

J Raman Spectroscopy

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“…The CARS model generalized to nonlinearly chirped laser pulses with asymmetric shapes is based on a previous work where the Raman molecule undergoing CARS interaction is conventionally identified according to the Fourier transform χ ( ω ) of the time‐dependent response function:

f_{R} ((), τ) = ϑ ((), τ) ({}, R_{nres} exp ((), i ϕ_{nres} - \frac{Γ_{nres} τ}{2}) + \sum_{r} R_{r} exp ([], - ((), i Ω_{r} + \frac{{normalΓ}_{r}}{2}) τ)),

where ϑ ( τ ) is the Heaviside step function needed to secure causality, R nres and R r are amplitude factors that depend on the particular Raman medium under study and they refer, respectively, to the nonresonant and resonant contribution to the response function. As to the latter, the spectral resonances typical of the CARS spectrum are numbered by the index r and characterized by the vibrational (or rotovibrational) frequencies Ω r whereas the inverse of Γ r measures the decay time of the r ‐th Raman coherence induced by means of the CARS interaction.…”

Section: Cars Model For Asymmetric Chirped Laser Pulsesmentioning

confidence: 99%

“…Next, considering the approximation of Equation , the polarization becomes

P_{CARS}^{(3)} ((), ω_{italicaS}) \propto \sum_{p_{1}, p_{2}, p_{3}} a_{1, p_{1}} a_{2, p_{2}}^{*} a_{3, p_{3}} e^{i β_{3, p_{3}} δ_{aS}} \int_{- \infty}^{\infty} \int_{- \infty}^{\infty} e^{- italicix ((), τ_{12, p_{1}} - β_{1, p_{1}})} e^{- italiciy ((), τ_{23, p_{2}} - β_{2, p_{2}} - β_{3, p_{3}})} e^{i ([], α_{1, p_{1}} x^{2} - α_{2, p_{2}} {(x - y)}^{2} + α_{3, p 3} {(δ_{italicaS} - y)}^{2})} χ ((), y) G_{1, p_{1}} ((), x) G_{2, p_{2}}^{*} ((), x - y) G_{3, p_{3}} ((), δ_{aS} - y) italicdxdy,

and the meaning of the approximations used in this work is now fully revealed. The asymmetry in the phase is simulated by means of a linear term that adds to the time delays, whereas the quadratic phase appears in combination with the Gaussian functions that define the ideal model treated earlier . Ultimately, the whole solution is derived from the result offered in the previous work valid for linearly chirped Gaussian laser pulses that form the integrand of the double integration of Equation .…”

Section: Cars Model For Asymmetric Chirped Laser Pulsesmentioning

confidence: 99%

“…Attempts at full comprehension of coherent anti‐Stokes Raman scattering (CARS) through analytical tools have accompanied from the very beginning the development of this field of research on Raman coherence . The theoretical effort has come a long way since those days and, after the advent of laser systems with ultrashort pulse durations, similar analytical attempts addressing the complications arising from chirped laser pulses have been made . Here, a further step is introduced.…”

Section: Introductionmentioning

confidence: 99%

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Reconstruction of coherent anti‐Stokes Raman scattering signals generated by means of laser pulses with asymmetric amplitude and phase

Marrocco

2019

J Raman Spectroscopy

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Time and frequency asymmetries in ultrashort chirped laser fields might appear as a consequence of dispersive propagation, pulse shaping techniques, or generation of auxiliary light pulses needed in nonlinear optics. Here, we try to find an answer to the question of how to solve analytically coherent anti‐Stokes Raman scattering (CARS) under asymmetric conditions of chirped femtosecond laser pulses. The approach breaks in two parts. One for the field amplitudes and the other for the phases. The former revolves around Gaussian dependences that, besides being rather common in ultrashort laser physics, can be arranged and mixed to reproduce spectrally asymmetric laser amplitudes. The latter is limited to field phases with cubic frequency dependence (i.e., second‐order chirp) whose asymmetry is simulated by adding a linear term to the quadratic phase. Both approximations for amplitudes and phases of the three laser pulses are mandatory to guarantee the solution to the complexity posed by the CARS problem. Comparisons with known experimental and numerical results support the validity of the model.

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“…In order to allow a meaningful evaluation, a novel Fourier analysis approach was developed permitting the determination of relative concentrations and temperatures. Another study related to gas phase and combustion diagnostics is authored by Marrocco . He extended his theoretical model not only to allow the investigation of effects caused by the temporal laser profile but also to include chirp.…”

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confidence: 99%